Needle Exchange Programs (NEPs) have emerged as important public health interventions in the fight against the spread of HIV infection among injection drug users and their sexual partners. While there is growing consensus that these programs are effective at slowing the spread of HIV and other blood-borne viruses, relatively little investigative attention has been directed at evaluating the ability of NEPs to engage drug users in needed, available, community-based drug treatment programs, health care and social services. The potential for NEPs to serve as a "bridge to treatment" is an important, yet untested, objective of needle exchanges and has important implications for their perceived role and future support. The proposed project will enroll and follow, at six month intervals, 250 randomly selected subjects from the Prevention Point Philadelphia needle exchange program, a program that exchanged over 700,000 syringes in 1996. Two comparison groups will be followed: 1) 250 non-exchangers-- IDUs who do not use the needle exchange will be recruited from areas with easy access to the existing NEPs and, 2) 250 potential exchangers-- IDUs from neighborhoods targeted for new NEP sites during the second year of study operations. All participants will be counseled about the need to utilize available services, including the needle exchange. Primary outcomes will be stability of NEP use and utilization of community-based drug treatment services. Secondary outcomes will include completion of HbV vaccination, and the incidence of HIV nd Hbv infection. The study will also collect extensive information regarding the attractions and barriers to these services. A qualitative component of this research will investigate, via qualitative interviews and participant observation, the ways in which needle exchange programs offer injection drug users access to services. This portion of the research will provide detailed information on the context of service utilization and the specific features of the needle exchange that enhance or inhibit linkages to services. Thus, the data from this study will not only provide an assessment of the impact of NEPs, but will also provide guidance regarding the enhancement of operational features of needle exchange programs. The Philadelphia community provides an important opportunity to carefully examine the questions being asked in this study. The needle exchange to be studied, Prevention Point Philadelphia, is officially sanctioned and funded by the Philadelphia Department of Public Health, which has been highly supportive of this research. Monitoring the use of the exchange will be facilitated by the fact that it is the only exchange in the city and is establishing an automated registration system. The program is one of the ten largest exchanges in the United States and operates sites in five neighborhoods, allowing access to large numbers of diverse study participants.